1. Introduction

Adhesives are indispensable materials that underpin a vast array of industrial applications by enabling the formation of reliable, durable joints critical to product functionality, structural integrity, and longevity. Among these applications, the packaging sector is one of the largest consumers of adhesives, demanding materials that not only exhibit exceptional mechanical robustness but also meet increasingly stringent environmental and sustainability criteria ^[1][2][3]. Historically, synthetic adhesives—predominantly petrochemical-derived polymers—have dominated this sector due to their superior adhesion performance, ease of processing, and cost-effectiveness. However, these materials pose significant environmental concerns related to their non-renewable origin, resistance to biodegradation, and potential ecological toxicity upon disposal or incineration, contributing to pollution and resource depletion. The urgent global imperative to mitigate environmental impact and promote circular economy principles has catalyzed a paradigm shift toward the development of sustainable, bio-based adhesive alternatives ^[4]. Renewable polymers derived from biomass offer promising pathways to reduce reliance on fossil fuels and decrease the carbon footprint of adhesive formulations. Within this context, bacterial nanocellulose (BNC), a highly pure microbial polysaccharide synthesized extracellularly by bacteria such as Gluconacetobacter xylinus, has emerged as an exceptional candidate for bio-adhesive reinforcement ^[5]. BNC is characterized by its nanoscale fibrillar network, which imparts remarkable tensile strength, high crystallinity, flexibility, and biodegradability. Furthermore, its capacity to form strong hydrogen-bonded networks enhances interfacial adhesion within polymeric matrices, thereby improving the mechanical and functional properties of bio-based adhesives ^[5]. Complementing BNC, aloe vera (Aloe barbadensis Miller) is a succulent plant whose mucilaginous gel is rich in bioactive polysaccharides, which exhibit intrinsic adhesive and film-forming properties ^[6]. The gel’s viscous nature and biocompatibility make aloe vera a valuable natural polymeric matrix for adhesive systems. The strategic integration of BNC and aloe vera in adhesive formulations leverages the synergistic interplay between nanofibrillar reinforcement and polysaccharide adhesion, potentially yielding bio-based adhesives with competitive performance metrics relative to their synthetic counterparts ^[7]. The goal of this study was to develop and systematically characterize a bio-based adhesive formulated from BNC and aloe vera, aiming to deliver mechanical performance and adhesion properties comparable to commercial synthetic adhesives while offering enhanced environmental sustainability. The research focused on optimizing adhesive formulations, evaluating their mechanical and interfacial properties on diverse substrates, and assessing their potential as sustainable alternatives for industrial applications, particularly in the packaging sector. Adhesive performance was systematically evaluated against a benchmark commercial synthetic adhesive through mechanical testing on substrates varying in surface roughness and physicochemical properties. This research directly addresses the rising regulatory and market-driven mandates—embodied by policies such as the European Green Deal—that promote sustainable material usage, reduction of environmental impact, and advancement of circular economy strategies. The principal objectives of this work were as follows: (1) to conduct an exhaustive market and literature review of adhesive technologies relevant to packaging; (2) to optimize the cost-efficient biosynthesis of BNC using agro-industrial by-products and alternative nutrient sources; (3) to develop and optimize aloe vera–BNC composite adhesive formulations; (4) to perform mechanical and adhesion strength testing on relevant substrates; and (5) to benchmark these bio-based adhesives against commercially available synthetic adhesives to assess their industrial viability.

2. Sustainable Nanocellulose-Aloe Adhesive Development for Packaging Applications

This entry is adapted from: https://doi.org/10.3390/molecules30153136